The wind is the major force of power in sailboat racing. Understanding the wind with all its variables, such as shifts, is necessary for success. The windshifts are classified along two distinct classes. Windshifts blowing across the water with a change in direction are called geographic shifts. Geographic shifts fall into three patterns: persistent, oscillating, or random. The second class of windshifts is the velocity or intensity of the shifts.
Understanding and predicting windshifts is one of the most intellectual and important aspects of sailboat racing. Not even NASA scientists care whether the wind will shift five degrees in the next minute, but to sailors this is a vital piece of information.
The key to using windshifts tactically is being able to predict with reasonable accuracy what is going to happen to the wind at any point throughout the race. The better your information concerning the wind, the more accurate and precise your expectations become. Therefore, windshifts are critical, if you have done your homework understanding the windshifts, you will have a better feel of what is to be expected from the wind and consequently will have the most fun and success in using the windshifts tactically.
According to prior art practice, one method of determining wind direction and shifting of the wind while sailing was to employ streamers or a wind vane mounted at various points of the sailboat. During the operation of the boat the wind direction device was continuously looked at for direction and changes or shifts therein. Such streamers and wind vanes were not accurate in showing the direction of the driving force wind. The wind direction was also modified by the speed and direction of the boat itself. Furthermore, with the boat itself angulated to the horizon, as it often is during sailing, the helmsman's difficulties are multiplied. The heeling and rocking of the boat changes the effective area against which the wind can operate on the vane. Therefore, the accuracy of the vane in determining the wind direction is greatly diminished.
In measuring the wind speed, it is assumed that the wind moves solely along the horizontal and along the surface of the earth. When a cup anemometer is used to measure the speed of the wind, wind shifts cause an erroneous reading. Most anemometers are based upon pivotal movement of the elements about an axis.